International Patent Application No. WO 2003/078945 A1 to Woolfrey (Woolfrey) describes the dual-beam calibration of a spectrometer. A laser beam is normally directed toward sample focusing optics, and is diverted away from its normal path to illuminate a first reference source.
International Patent Application No. WO 2013/163268 A1 to Workman (Workman) describes a spectrometer secondary reference calibration. The spectrometer is designed to perform a measurement on a sample. To perform a diagnostic measurement, secondary reference samples are provided in a turret or paddle inserted mechanically into a measurement chamber of the spectrometer.